Tunnel kiln



P. DRESSLER Aug. 16, 1960 TUNNEL KILN 2 Sheets-Sheet 1 Filed Aug. 19, 1955 LO 5N IN V EN TOR.

PHIL/P DRESSLER A T'TORNE Y Aug.. 16, 1960 P. DREssLER 2,948,945

TUNNEL KILN v Filed Aug. 19, 1955 2 Sheets-Sheet 2 IN V EN TOR. PHIL/P DRESS LER A7TORNEY TUNNEL KILN Philip Dressler, f3.0. Box 1888, Pittsburgh, Pa.

Filed Allg. 19, 1955, ser. N0. `529,411

8 Claims. (Cl. 21S-142) The general object of the present invention is to provide an improved method of and improved apparatus for salt glazing ceramic ware. The desirability of salt glazing sewer pipes and other ceramic ware has long been recognized and various methods and apparatus for the purpose have been devised and some of them have been put into commercial use.

Most of the salt glazing methods heretofore used have involved the evaporation of solid salt to form salt vapors which are brought into Contact with the ware to be glazed while those wares are being fired and are at or near their maximum firing temperatures. However, the introduction of solid salt into a tunnel kiln firing chamber by injection into a burner space as known prior to my present invention, is open to the practical objection that the evaporation of the salt supplied to the kiln is ordinarily incomplete, with the result that some solid salt particles deposit on and corrode the exposed kiln and kiln car surfaces. Moreover, some of the solid salt particles are deposited on the ware and thereby give the latter an undesirably rough surface instead of the smooth surface which the salt glazing operation is intended to produce.

To minimize the objectionable effects of salt particles depositing on the hot kiln surfaces and kiln cars in the kiln, there has been a limited use of provisions for evaporating solid salt in auxiliary 'furnaces or iire boxes which are adapted to' pass salt vapors into the kiln chamber. The use of such auxiliary furnaces or boxes iS o'pen'to'seriou's objection, however, because of the practical-necessity of'continuously maintaining a salt evaporating condition in said furnaces or boxes. To lmeet this situation, it was proposed inthe Robson-Patent 2,514,143 'of July 4, 1950, to Vmake each auxiliary furnace or salt evaporating box removable to facilitate its Yrepair or re- .placement when its refractory lining has been destroyed by 'corrosive action of the salt. While some commercial use of :the Robson patent has been made, the Robson apparatus is disadvantageously characterized byits provisions for continuously withdrawing salt vapor from the evaporating boxes into `the kiln, and the subsequent withdrawal of salt vapor from the kiln atlpredetermined kiln points. Such continuous withdrawal o'f vapor robs the kiln of a great deal of heat which with niy present invention, may advantageously be used in preheating the ware.

My present invention is characterized by simple and effective provisions which I have devised for continuously maintaining a kiln box or boxes in open communication with Vthe kiln, while at the same time effectively preventing the passage of salt glazing -material into' the kiln gas stream from saidkiln box or boxes during each of regular periods in which the passage of salt glazing material into the kiln is interrupted. Y

The various features `of novelty which characterize my invention are pointed out with particularit'y in the claims annexed to and forming a part of this speciiication. For la'better understanding df the invention, however, its ad- '-2 vantages, and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and'described preferred embodiments of the invention.

Of the drawings: j y

Fig. 1 is a horizontal Vcross section diagrammatically illustrating a direct red continuous kiln with auxiliary salt glazing boxes in operative association with the kiln;

Fig. 2 is a section taken on the line 2 2 of Fig... 1B and showing the Vgeneral structure of one of the kiln boxes;

Fig. 3 is an enlarged reproduction of a portion of'the structure shown in Fig. 4; j

Fig. 4 is an elevation'in section on the line 4--4 of Fig. l;

Fig. 5 is a sectional view taken along the line 5 5 of Fig. 1;

Fig. 6 is an elevation illustrating a modification of the apparatus shown in Figs. 3 and 4; and

Fig. 7 is a sectional elevation of a modification of the boxes shown in Fig. 4.

In the drawings I have diagrammatically illustrated a continuous tunnel kiln 1 including provisions for periodically passing streams of glazing fluid into the kiln through boxes S and S at opposite sides of the kiln during brief periods. Those periods alternate with longer periods during which all, o'r substantially all ofthe heating fluid passed into the kiln is utilized in increasing the kiln temperature. The kiln 1 may well be of the known circular type, but as shown, the kiln 1 is a straight kiln with conventional meansrfor continuously advancing a train of kiln cars 2 from the inlet end 3 to the outlet end 4- of the kiln. Air is passed into the kiln at its outlet end 4, and air and products of combustion are discharged at the kiln inlet end 3. The cars in the kiln form a continuous train extending from the inlet end to the outlet end of the kiln. The portion of the kiln adjacent its inlet end 3, acts as a preheating zone A, and the portion of the kiln adjacent its outlet end 4 acts as a cooling zone C, and the intermediate section of the kiln constitutes a burning or firing zo'ne B. n

The kiln cars 2 are supported by wheels S running on track rails 6 which extend from one end to the other end of the kiln. The wares to be red, such as sewer pipes or analogous bodies, are mounted on the platforms 7 of 'the cars in the kiln ware space '8. A chamber V9` at eachV "side of the ware` space 8 receives burning gases entering the chamber 9 through vertical spaces 10 in the side wallsof the kiln. An uprising refracto'ry wall portion or body 11 of the `kiln structure is interposed between each kiln chamber 10 and the adjacent car platforms V7. The lower portion of each chamber l0 is in communication with a salt evaporating chamber 12 in a box at 'the adjacent side of the kiln structure. As shown, the `box at the lupper side of the kiln, as seen in Fig. 1, is designated S, and the box at the other side of the kiln is designated S. Each of the boxes S and S is supported by wheels` 12a running on track rails 12b 'at right angles to the kiln 1.

Each box S is formed with horizontal inlets 13 and 13a. The inlet 13 may be perpendicular to the length of the kiln but as shown, is parallel to the adjacent side of the kiln. Each inlet 13a is transverse to the inlet passage 13. Burners 14 and 14a discharge burning gas into the inlets 13 and 13a, respectively. A curved pipe 15 is formed with an uprising, inlet end receiving salt passed through the pipe 15 into the inlet 13'. A `trough 16 receives salt throl'lgh the bottom outlet pipe 17 of a salt hopper 18. An agitator 19 extending into the outlet .pipe 17 is given vertical movements by a vibrator element A20.* Burning gases may be passed into theV lbox S through the inlet 413a as through the inlet 13. During 3 t. the glazing periods salt is fed into the chamber 12 through an inlet 13b in the wall portion of the box S directly above the gas passage 12 leading to the kiln chamber 10.v

In the form of the invention shown by way of example in Fig. 4, the chamber 12 of the box S is formed with an outlet passage including a short horizontal upper end portion 21, and a lower, elongated, downilow conduit 22. The lower end of the conduit 22 may advantageously terminate at a level intermediate the upper and lower edges of the track rails 6. In its normal operative position, the llower end of the conduit 22 is above and in register with, and in close proximity, to the upper end of a stationary vertical conduit 23. The normally adjacent ends of each associated pair of conduits 22 and 23 may include relatively wide upper and lower circular flanges 24 and 25 at the adjacent ends of the conduits 22 and 23, to thereby minimize leakage through the thin space between the adjacent flanges. As diagrammatically shown in Fig. 4, the lower end of the conduit 23 is connected to an underground pipe 26.

The only significant difference between the boxes S and S' shown in Fig. l, is the location lot the conduit elements 21, 22, 23, 24 and 25 in front of the kiln passage 12, and the location of the corresponding conduit elements 21-25 lat the rear of the kiln passage 12 of the box S. The relative yarrangement of the parts 21-25 and the parts 21-25 permits the conduits 25 and 25' to be connected to separate underground pipe sections 26 and 26', respectively, which are laterally displaced from one another, and yare separately provided with cut-olf valves 27 and 27', respectively. As shown in Fig. l, the outlets of the valves 27 and 27 are connected through a single pipe 28 to a damper house 29. The underground piping arrangement described thus permits either one of the boxes S and S' to be temporarily disconnected from the damper house without simultaneously disconnecting the other box from the damper house. In normal operation, the cut-off valves 27 and 27 will be closed during relatively short glazing periods which alternate with longer periods in which no significant amount of gases Hows into the kiln from the boxes S and S'.

In yaddition to the pipe 28 passing gases from `the boxes S and S to one inlet of the damper house, gases are passed from the kiln into the damper house 29 through pipes 30 and 32. The pipe 30 passes gases to the damper house from salt fume outlet chambers or lines 31, and the pipe 32 passes exhaust gases to the damper house from exhaust chambers or flues 33. The flues 33 are adjacent the entrance end 3 of the kiln. The exhaust flues or chambers 31 are between the flues 33 and the boxes S and S and substantially nearer to said boxes than to the lines 33. As those skilled in the art will recognize, the passage of gas into the damper house 29 through the pipes 26, 26', 30 4and 32, may be regulated as conditions make desirable. The gases entering the damper house 29 through its different inlets, pass to an exhaust fan 34 having an outlet 35 normally connected to a stack, not shown, which passes fumes into the atmosphere.

As has been made apparent, the apparatus shown in Figs. l to 4 and described above, is characterized by a draft switching arrangement which permits the salt bearing combustion gases entering the furnace zone to be drawn olf during the salting period, and at the conclusion of the salting period permits all of the products of combustion to be drawn from the kiln in the normal Way, so as to take advantage of the heat in the gases topreheat the ware passing into the kiln at its entrance end. 'I'he apparatus disclosed in the prior Robson Patent 2,514,143 includes no effective means for withdrawing the salted gases from the kiln. In consequence, it is necessary to continually bleed hot gases from the furnace zone of the kiln, so that much heat is necessarily withdrawn from 4 the kiln, thus robbing the kiln of a great deal of heat which with my invention can be used in preheating the ware.

From the foregoing, it is clear that there are brief periods during Which salt fumes are intentionally introduced into the kiln to glaze the ware therein and there are other longer periods when it is desired to prevent salt fumes from entering the kiln. During .the non-salting period, it is my present invention to withdraw gases from the salting tire boxes to prevent these gases, which are salt fume bearing, from passing into the gas stream of the kiln. Accordingly, during the non-salting period, the main stream of kiln gases may be passed to the entrance end 3 of the kiln with no deleterious effects. Heretofore, it has been necessary to bleed olf some of the main gas stream before it reached the preheating zone in order to get rid of the salt fumes. This bleeding action naturally drew oil hot gases useful for preheating Ithe ware at the entrance end. However, by withdrawing the gas from the salting fire boxes themselves, all of the hot gases in the main gas stream of the kiln may be carried to the entrance end `and thus be employed to preheat the ware. Of course, during the salting periods, all the salt laden fumes generated in the salting re boxes should fbe passed into the kiln. To accomplish these results, means for withdrawing gases from the salting fire boxes should operate during non-salting periods and should be inactive during salting periods. This is accomplished by closing `a darnper controlling the ow of gases from the salting tire boxes to an exhaust during the salting period and opening said damper during the non-salting period.

In the use of the form of the invention shown in Figs. l, 2, 4 and 5, the damper house inlets shown in Figs. 1 and 2 require no departure from customary construction, except for the addition to the damper house 29 of the conduit 28 and its valve outlet. The dampers or valves 30a and 32a associated with the conduits 30 and 32, respectively, require no essential modification of kiln appanatus which includes no salt glazing provisions.

vIn the use of my invention illustrated in Figs. l to 4, the damper 28a connecting the damper house 29 to the conduit 28 is closed, the damper 30a controlling the outow from the salt fume exhaust chamber 31 is open, and the damper 32a connecting the exhaust chamber 33 adjacent the entrance end of the kiln is partially closed during each salting operation. When each salting operation is concluded, damper 30a is closed, damper 28a is moved into its normal open operating position, 'and damper 32a is opened to the extent needed to draw the gases toward the entrance end 3 of the kiln.

The apparatus shown in Fig. 6 difers from the type of apparatus shown in Fig. 4, essentially only in that the conduit elements 21-25 and 21'425 shown in Figs. 2 and 4 fare replaced in Fig. 6 by conduits 2lb and 22b which directly connect the kiln chamber 10 to piping of the general character shown in Fig. 6. The outlets 21 and 21 from the chambers 12 and 12 of Fig. 4 are replaced, in the type of apparatus shown in Fig. 6, by outlet channels 2lb and 22b which directly connect the kiln chamber 10 to associated underground conduits which may be like the conduits 26 and 26.

Fig. 7 illustrates a salting box SB diien'ng more Widely from the boxes previously described. The box SB has an outlet 36 opening into the lower end portion of an associated kiln chamber 10. Fuel gas is supplied to the box SB through an upper port 37 and a lower port 38, each in the wall 39 of the box SB which is parallel to, and most remote from the side of the kiln into which the port 36 opens. Burning gas is passed into the box SB through the upper port 37 by a gas burner 40, and through the lower port 38 by a gas burner 41. Salt glazing material is passed into the box SB through a port or opening 42 in the top wall of the box. The box SB is supported by wheels 43 running on track rails l d4 which are transverse to the kiln, as are the previously mentioned wheels 12a and track rails 12b. During the periods in which the passage of gas into the kiln chamber through the outlet 36 from the boX SB is interrupted, gas may be withdrawn from the box SB through one or more outlets 45 analogous to the outow passages 21 and 22 shown in Fig. 4.

While in accordance with the provisions of the statutes, l have illustrated and described the best forms of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the forms of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. In combination, a kiln having a preheat zone, a burning zone and a cooling zone through which ware passes in successive order, exhaust means for withdrawing gases from said kiln, a rst duct means having an inlet disposed adjacent the border between the preheat zone and the burning zone of said kiln and having an outlet operatively connected to said exhaust means, salt vapor generating means movable relative to said kiln to and from an operative position adjacent said burning zone, a second duct means for conveying salt vapor from said salt vapor generating means to said burning zone when said salt vapor generating means is in said operative position, a third duct means having an inlet connected to said salt vapor generating means and an outlet operatively connected to said exhaust means, damper means for controlling the flow of gases in said duct means from their respective inlets to said exhaust means, said damper means including means for opening said iirst duct means and closing said third duct means whereby to permit salt vapor generated in said salt vapor generating means to pass into said burning zone of said kiln through said second duct means and out through said rst duct means along with hot gases in said burning zone, and for closing said first duct means and opening said third duct means whereby to draw olf salt vapor from said salt generating means and thereby prevent it from passing into said burning zone of said kiln through said second duct means.

2. The method of salt glazing ceramic articles in the firing zone of a kiln, comprising the steps of continuously generating salt vapors outside of said kiln, periodically introducing said salt vapors into said firing zone, and during alternate periods drawing off said salt vapors prior to their introduction into said iiring zone to prevent their introduction into said ring zone.

3. The method of salt glazing ceramic articles in a kiln having a preheat zone and a firing zone, comprising the steps of continuously generating salt vapors outside of said kiln, periodically introducing said salt vapors into said iin'ng zone and concurrently drawing olf said vapors before they enter said preheat zone, and during alternate periods drawing off said salt vapors prior to their introduction into said firing zone to prevent their introduction into said ring zone.

4. In combination with a kiln having a firing zone for ring ceramic wares, a salt vapor generator removably disposed adjacent said kiln, said salt vapor generator being provided with a salt evaporating chamber, a fuel burner associated with said salt vapor generator for heating said salt evaporating chamber to salt Vaporizing temperatures, rst duct means extending between said salt evaporating chamber and said firing zone of said kiln for permitting the flow of salt vapor into said tiring zone from said evaporating chamber, negative pressure means, second duct means having an inlet disposed between said salt vaporizing chamber and said firing zone and an outlet connected to said negative pressure means, and means for opening and closing said second duct means for permitting said negative pressure means to draw oil salt vapor generated in said salt vaporizing chamber through said second duct means to prevent the introduction of salt vapor into said firing zone through said rst duct means and for preventing said negative pressure means from drawing off said salt vapor to thereby permit the introduction of said salt vapor into said ring zone through said first duct means respectively.

5. The method of salt glazing ceramic wares in a kiln having a preheat zone and a ring zone, comprising the steps of continuously generating salt vapor outside of said kiln, periodically introducing said salt vapors into the tiring zone of said kiln and at the same time drawing olif said vapors before they reach said preheat zone, and during alternating periods drawing off said salt vapors prior to their introduction into said tiring zone to prevent their introduction into said firing zone and at the same time permitting substantially all gases in said firing zone to iiow into said preheat zone.

6. Salt glazing apparatus for ceramic articles, including a kiln having a preheat zone and a burning zone, means removably disposed adjacent said kiln for generating salt vapor, means for permitting the discharge of salt vapor into said burning zone at spaced time intervals, and means including a duct in direct communication with said salt generating means and operable during the alternating intervals for preventing said salt vapor from entering said burning zone of said kiln by drawing olf said salt vapor through said duct.

7. Salt glazing apparatus for ceramic articles, including a kiln having a preheat zone and a burning zone, means disposed adjacent said kiln for generating salt vapor, said kiln being provided with a passage having an inlet in communication with said salt generating means and an outlet in communication with said kiln burning zone for passing salt vapor from said salt generating means to said kiln, and means for preventing the passage of salt vapor into said burning zone, said last mentioned means including a duct having an inlet in communication with said salt generating means between said salt generating means and said outlet of said passage, said duct being adapted to draw off said salt vapor whereby to prevent its passage into said burning zone.

8. In combination a kiln having a burning section to heat ware therein, a salt vapor inlet duct having an outlet in direct communication with the burning zone of said kiln, a salt vapor generator unit removably supported adjacent said kiln and having a vapor outlet connected to the outer end of said salt vapor inlet duct, said generator unit including a combustion and vaporizing chamber, a fuel burner directed into said chamber, means for feeding salt into said chamber, a separate outlet from said chamber, and means for opening and closing said separate outlet for the discharge of vapor from said chamber to thereby prevent vapor from entering said burning section by drawing off the vapor through said separate outlet and to permit vapor to enter said burning section throught said vapor inlet duct, respectively.

References Cited in the le of this patent UNITED STATES PATENTS 1,556,208 Dressler Oct. 6, 1925 1,919,322 Dressler July 25, 1933 2,307,322 Ladd Ian. 5, 1943 2,514,143 Robson July 4, 1950 

